Delivery Systems

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For more than six decades, the United States has emphasized the need for a nuclear force that credibly deters adversaries, assures allies and partners, and would achieve U.S. objectives should deterrence fail. Since the 1960s, these objectives have been met by the U.S. nuclear triad through forces operating at sea, on land, and in the air. Today’s nuclear triad consists of: 14 ballistic missile submarines (SSBNs) armed with 240 submarine-launched ballistic missiles (SLBMs); 400 land-based intercontinental ballistic missiles (ICBMs); and 60 nuclear-capable heavy bomber aircraft capable of delivering gravity bombs and cruise missiles.

These strategic forces are enabled by secure nuclear command, control, and communications (see Chapter 2: Nuclear Weapons Employment Policy, Planning, and NC3) and supplemented by a small number of non-strategic nuclear forces that provide an ability to forward deploy weapons in Europe and globally.

This chapter provides an overview of current and planned U.S. nuclear delivery systems and platforms. Figure 3.1 offers an overview of current nuclear weapons and delivery systems.

Figure 3.1
Note: B = Bomb W = Warhead
Figure 3.1 Current U.S. Nuclear Deterrent
(Delivery systems and associated
nuclear weapons)

Complementary Attributes of the U.S. Nuclear Triad

Each leg of the triad provides unique and complementary attributes. Collectively, the triad seeks to ensure that no adversary believes it could launch a strategic attack that eliminates the ability of the United States to respond and inflict unacceptable damage-for any reason, under any circumstances.

SSBNs are survivable. A portion of the SSBN fleet is always on patrol, making it very difficult to track U.S. ballistic missile submarines, which means they are highly survivable. ICBMs are responsive. ICBMs are deployed in hundreds of nuclearhardened silos and can be launched to reach targets within minutes, creating a complex targeting problem for adversaries. U.S. strategic bombers are a “show of force.” Bombers are a clear and visible signal of U.S. intent and resolve during a crisis and provide a variety of deployment and yield options. Bombers may also be recalled.

Eliminating a leg of the triad would weaken the combined strength of the force and simplify adversary attack planning. Also, the diversity of the triad enables risk mitigation if a particular leg of the triad is degraded or unavailable.

Currently, all three legs of the nuclear triad will undergo modernization at roughly the same time. Because of the tight schedule between the expected retirement of the legacy systems and the fielding of the replacement systems, the DoD, as a top priority, is committed to keeping these programs on track.

The combination of the advanced age of U.S. weapon delivery systems and current efforts to revitalize all three legs of the nuclear triad present challenges to the future U.S. nuclear deterrent. Every U.S. delivery system has had to remain in service far beyond its expected lifespan-by several decades, in some cases.

As many of these platforms reach an age at which their lives cannot be further extended, the United States is working to field new platforms and delivery vehicles on all three legs of the triad simultaneously. These replacement projects are time-sensitive; their current schedule has been described by senior DoD leaders as “just-in-time” delivery. Figure 3.2 illustrates the aging legacy delivery systems and the current plan for initial replacement (first unit deployed).

System Year First Deployed Original Design Life Projected First
System Age
at Initial
1981 30 years 2031 ~42 years*
Minuteman III
1970 10 years 2029 ~60 years
B-2A Bomber 1993 No set life; dependent
on flight hours/
airframe viability
TBD (replaced
as B-21 comes
~35 years
AGM-86 ALCM 1982 10 years Early 2030s ~50 years
F-15E DCA 1988 No set life; dependent
on flight hours/
airframe viability
available in
~40 years
* Each Ohio-class SSBN is being evaluated on a case-by-case basis and will be retired at end of life.
Figure 3.2 Legacy Delivery Systems Aging and Replacement

Nuclear Weapon Delivery Systems

A nuclear weapon delivery system is the military platform and delivery vehicle1 by which a nuclear weapon is delivered to its intended target in the event of authorized use (by the President of the United States, who retains sole authority to employ nuclear weapons). Most nuclear weapons have been designed for a specific delivery system, making interoperability potentially challenging.

In addition to the U.S. mix of silo-based Minuteman III (MMIII) ICBMs, Trident II D5 Life Extension (LE) SLBMs carried on Ohio-class SSBNs,2 and B-2A and B-52H nuclear-capable heavy bombers, the U.S. nuclear force includes dual-capable aircraft (DCA), that can carry conventional or nuclear weapons.


Nuclear-powered Ohio-class SSBNs (Figure 3.3) carry Trident II D5 LE missiles armed with W76-0/1/2 and W88 warheads. SSBNs are considered the most survivable leg of the nuclear triad because of their ability to transit and hide in the ocean depths, coupled with the long range of the missiles. Continuously on patrol, SSBNs provide a worldwide launch capability, with each patrol covering a target area of more than one million square miles. The intercontinental range of the SLBM and constant readiness allow U.S. SSBNs to hold targets at risk from their launch areas in the Atlantic and Pacific oceans.

Figure 3.3
Figure 3.3 Ohio-class SSBN USS Rhode Island

As the virtually undetectable undersea launch platforms for intercontinental missiles, Ohio-class SSBNs were built by the Electric Boat Division of General Dynamics, based at Groton, Connecticut. Eighteen Ohio-class submarines were built and commissioned between 1981 and 1997; thus, the average age is currently over 30 years old, and there are plans to extend the submarines up to 42 years of age.

The SSBNs of the Pacific Fleet are based at Naval Base Kitsap in Washington, and those of the Atlantic Fleet at Naval Submarine Base Kings Bay in Georgia. On average, submarines spend 70 days at sea, followed by 25 days in dock for overhaul.

The U.S. Navy operates a total of 18 Ohio-class submarines which consist of 14 ballistic missile submarines and four cruise missile submarines (SSGNs) that no longer carry nuclear weapons. The United States continues to take the necessary steps to ensure that Ohio-class SSBNs remain operationally effective and survivable until their replacement.

The Columbia-class SSBN is the replacement for the Ohio-class SSBN. The first Columbia-class submarine is scheduled to begin construction in 2021 and enter service in 2031. The Navy is planning to build 12 SSBNs, which are scheduled to remain in service until the 2080s. Each Columbia-class SSBN will be equipped with 16 missile tubes.

Current U.S. planning is for the number of SSBNs available for deployment to be reduced by two during the 2030s as the Ohio-class SSBN retires and the Columbia-class SSBN completes production.

Submarine-launched ballistic missiles have been an integral part of the strategic deterrent for six generations, starting in l956 with the U.S. Navy Fleet Ballistic Missile (FBM) Polaris (A1) program. Since then, the SLBM has evolved through Polaris (A2), Polaris (A3), Poseidon (C3), Trident I (C4), and today’s force of Trident II (D5). In 2017, the Trident II force began deploying the Trident II life extension (LE). This SLBM will be deployed on both Ohio- and Columbia-class SSBNs. Each SLBM program has been continuously deployed as a survivable force and has been routinely operationally tested and evaluated to maintain confidence and credibility in the deterrent.

Each Ohio-class SSBN carries 24 Trident II D5 LE missiles. The Trident II D5 LE missile is a three-stage, solid-propellant, inertially guided ballistic missile with a range of more than 4,000 nautical miles, or 4,600 statute miles. Trident II D5 LE is launched by the pressure of expanding gas within the launch tube. When the missile attains sufficient distance from the submarine, the first stage motor ignites, the aerospike extends, and the boost stage begins. Within about two minutes, after the third stage motor kicks in, the missile is traveling in excess of 20,000 feet (6,096 meters) per second.

Trident II was first deployed in 1990 and is planned to be in the inventory beyond 2020. The Trident II missile is also provided to the United Kingdom (UK), which equips the missile with UK nuclear warheads and deploys the missile on four UK nuclear-armed submarines that provide the UK Continuous- At-Sea-Deterrent (CAS-D).

Additionally, the United States has modified a small number of existing SLBM warheads to provide a low-yield option. The United States is also planning to pursue a modern nuclear-armed sea-launched cruise missile (SLCM). This will provide additional diversity in platforms, range, survivability, and assurance to allies.

Trident II has been deployed for more than 30 years. It is currently in the early stages of a life extension which will extend its deployment until 2042. This life extension will match the Ohio-class submarine service life and serve as the initial baseline SLBM through the introduction of the Columbia-class. The U.S. Navy will begin studies in 2020 to define requirements for the future SLBM (D5 LE2) planned to be deployed through the service life of the Columbia-class (through 2080).


Intercontinental ballistic missiles, which are launched from hardened silos buried in the ground, are high-yield, accurate, on continuous alert, provide immediate reaction if necessary, and can strike their intended targets within 30 minutes or less of launch (see Figure 3.4).

Figure 3.4
Figure 3.4 Unarmed MMIII ICBM Launch during an Operational Test at Vandenberg AFB, CA

ICBMs are the most responsive leg of the triad because they are always ready and can be launched within minutes on Presidential authority. U.S. ICBMs provide deterrence against a first strike by an adversary because no adversary can be confident in its ability to destroy all U.S. ICBMs prior to their being launched.

Starting in January 1951, when the Air Force directed a $500,000 study for the development of an ICBM capable of delivering an atomic bomb, known as “Project Atlas,” ICBMs have underpinned the U.S. nuclear deterrent. From 1959–1965, the Atlas was deployed at different Air Force bases stretching from upper New York State all the way to New Mexico. The majority of the Atlas ICBMs were stored vertically in aboveground launchers. From 1962–1987, two versions of the Titan, I and II, were deployed. The Titan was the largest ICBM ever deployed and held a nine megaton nuclear warhead, making it one of the most powerful nuclear weapons in U.S. history.

When Minuteman became operational in 1962 and began to replace Titan, it was the first solid-fueled ICBM ever deployed, and this technology brought about a revolution in missile development. There have been four versions of the Minuteman, the IA, IB, II and III. Additionally, the Peacekeeper ICBM was deployed from 1987 until 2005 and held up to ten nuclear warheads each. Although the START II arms control agreement never entered into force, Peacekeeper was removed from the ICBM force in anticipation of the treaty’s ratification.

The Minuteman III ICBM was first deployed in 1970, with a planned ten-year service life. A series of life extension programs have kept MMIII viable. For the ten-year period between 2002–2012, MMIII underwent a life extension program intended to keep the system fielded until 2030. By 2030, and after 60 years of operation, MMIII will be the oldest deployed strategic ballistic missile in the world as it begins to be replaced by the ground-based strategic deterrent (GBSD) ICBM.

Today, the U.S. ICBM force consists of 400 single-warhead MMIII missiles, armed with W78 and W87-0 warheads. If authorized by the President, MMIII could carry up to two additional warheads. MMIII missile bases are located at F.E. Warren Air Force Base (AFB) in Wyoming, Malmstrom AFB in Montana, and Minot AFB in North Dakota. The United States has initiated the GBSD program to begin the replacement of MMIII in 2029. The GBSD program will also modernize the 450 ICBM launch facilities that will support the fielding of 400 modern ICBMs, to be armed with W87-0 and W87-1 nuclear warheads.

The GBSD program will replace the MMIII with a modern ICBM, revitalize the command and control architecture, and recapitalize the associated infrastructure. The GBSD program is currently in the technology maturation phase. GBSD is scheduled to enter service by the early 2030s and will be deployed until the 2070s.


The U.S. bomber force serves as a visible, flexible, and recallable national strategic asset. Bombers provide a rapid and effective hedge against technical challenges that might affect another leg of the triad and offset the risks of geopolitical uncertainties. Furthermore, nuclear-capable bombers are important to maintain extended deterrence against potential attacks on U.S. allies. The ability to forward deploy heavy bombers, especially in Europe, signals U.S. resolve and commitment in a crisis and enhances the reassurance of U.S. allies, strengthening regional security architectures. The bombers also play a critical role in the U.S. hedging strategy, given their ability to upload additional weapons, bombs, and nuclear airlaunched cruise missiles (ALCMs) in response to possible geopolitical surprises. The upload potential of the U.S. bomber force also provides an important hedge against programmatic risk in the strategic replacement programs (i.e., if any of the nuclear delivery system replacement programs are late).

The nuclear B-52H force is located at Barksdale AFB in Louisiana and Minot AFB in North Dakota. The B-52H fleet has been the backbone of the strategic bomber force for more than 50 years. The B-52H Stratofortress (Figure 3.5) is a heavy, long-range bomber that can perform a variety of missions. It is capable of flying at subsonic speeds at altitudes of up to 50,000 feet and can carry precisionguided conventional ordnance in addition to ALCMs armed with W80-1 warheads. B-52H bombers carry six AGM-86B/C/D ALCM missiles on each of two externally mounted pylons and eight internally on a rotary launcher, giving the B-52H a maximum capacity of 20 missiles per aircraft. Beginning in 1982, B-52H bombers were equipped with ALCMs in response to steady advances in adversary air defense systems. This way, the B-52 can launch its nuclear weapons without having to penetrate adversary defenses, as it would have to do in order to deliver nuclear gravity bombs.

Figure 3.5
Figure 3.5 B-52H Stratofortress

The Long Range Stand Off (LRSO) cruise missile will replace the aging ALCM with a modern cruise missile capable of holding targets at risk, even in heavily defended airspace. The LRSO is currently in the development phase and scheduled to be fielded in 2030. The LRSO, armed with W80-4 nuclear warheads, will enable the B-52H to remain an effective part of the nuclearcapable bomber force and preserve its upload potential as a key hedge against unforeseen technical and geopolitical challenges. Also critical to the heavy bomber force is a viable aerial refueling capability, which is undergoing recapitalization now, with the KC-46 Pegasus currently being produced.

The Air Force is modernizing the B-52 bomber to remain a viable long-range strike platform for its extended life. These upgrades include replacement of the current engines, integration with modern digital munitions, and replacement of various avionics systems.

The B-2 Spirit stealth bomber (Figure 3.6) entered the force in 1997, enhancing U.S. deterrent forces with its ability to penetrate adversary air defenses. The B-2A bomber is now the only long-range, nuclear-capable U.S. aircraft that can penetrate advanced air defenses. The B-2 is a multi-role bomber capable of delivering both conventional and nuclear munitions, including B61-7/11 and B83-1 nuclear bombs until their planned retirement in the mid-2020s, after which, the B-2 will carry the B61-12. The B-2 force is located at Whiteman AFB in Missouri.

Figure 3.6
Figure 3.6 B-2 Spirit

The United States will sustain and modernize the B-52H and B-2A to ensure they remain effective into the future. Given the continuing proliferation and improvement of adversary air defense capabilities and the continued aging of the B-52H, ALCM, and B-2A, the United States has initiated a program to develop and deploy the next-generation bomber, the B-21 Raider. The B-21 will be a long-range, stealth strategic bomber with the ability to deliver conventional and nuclear weapons, to include the B61-12 bomb and the W80-4 nuclear warhead on the LRSO. The plan is for a 100-aircraft fleet to begin entering service in the mid-2020s. For its nuclear mission, the B-21 will be capable of delivering both gravity bombs and the new LRSO cruise missile.

In addition to the nuclear strategic triad, the United States maintains a fleet of F-15E Strike Eagle dual-capable aircraft (DCA) (Figure 3.7). These DCA are based in the continental United States (CONUS) and also forward deployed in Europe. DCA are able to deliver conventional munitions or B61-3/4/10 nuclear bombs. The forthcoming B61-12 gravity bomb will replace earlier versions of the B61 and will be available in the early to mid-2020s. DCA are available to support the North Atlantic Treaty Organization (NATO) in combined-theater nuclear operations.

Figure 3.7
Figure 3.7 F-15E Strike Eagle

The United States is incorporating a nuclear capability into the F-35 as a replacement for the current aging DCA force. Plans for initial fielding of the nuclear-capable F-35 is 2025. Several NATO allies also provide DCA capable of delivering U.S. forward-deployed nuclear weapons.

The forward presence of dual-capable aircraft contributes to the deterrence of potential adversaries and the assurance of allies. If necessary, the United States has the ability to deploy DCA and nuclear weapons to other regions, such as Northeast Asia.

Figure 3.8 shows U.S. current and planned near-future delivery systems and associated platforms and nuclear weapons.

Figure 3.8
Figure 3.8 Current and Near-Future Nuclear Deterrent

1 The terms nuclear weapon delivery system, nuclear delivery vehicle, and nuclear weapon platform or nuclear platform are often used interchangeably. For the purposes of this handbook: (a) a nuclear weapon delivery system is the mating of the military platform and the delivery vehicle to form the system (e.g., Trident II D5 LE on Ohio-class SSBN); (b) a delivery vehicle is the portion of the weapons system which provides the means of delivery of a nuclear weapon to its intended target (e.g., nuclear cruise missile, Trident II D5 LE missile); and (c) a nuclear platform is any structure or system on which a weapon can be mounted/loaded (e.g., ballistic missile submarine). ICBMs are both a delivery platform and a delivery vehicle.

2 The SSBN acronym stands for “Ship, Submersible, Ballistic, Nuclear.” However, the SSBN is more commonly referred to as ballistic missile submarine or fleet ballistic missile submarine.